The Parallel Decision Feedback and Feedforward Equalizer

We illustrate a new type of nonlinear equalizer, obtained by placing a decision feedback equalizer and a decision feedforward equalizer in parallel. This type of equalizer, called a "parallel decision feedback and feedforward equalizer" or, briefly, a "composite equalizer," is characterized by substantially reduced error propagation if the eye diagram is open at the input of the decision device of the decision feedback equalizer and of the first decision device of the decision feedforward equalizer. The composite equalizer may be conveniently built up using a single decision device in the decision feedforward equalizer.